added documentation for 4 AVbus modules:
     1MB SRAM module
    64MB SDRAM module
    16MB FLASH module
    Communications/Memory module containing
         1MB SRAM
        64MB SDRAM
        16MB FLASH
        10/100/1000 ethernet PHY
        IrDA
        USB2
        PC Card (PCMCIA)
        I don't see it in this guide but my board has empty DIP location for Bluetooth module
            Mine is in storage, as are printouts of my PDF guide for it. Will update someday
            to that, I found these copies on general internet as Avnet has dropped it.
Merge pull request #1 from amigabill/master

Documentation for Avnet Spartan 3 PCI card addons